Partitioning of charged and neutral dextran-dye derivatives in biphasic cellulose nanocrystal suspensions

2008 ◽  
Vol 86 (6) ◽  
pp. 503-511 ◽  
Author(s):  
Stephanie Beck-Candanedo ◽  
David Viet ◽  
Derek G Gray
Keyword(s):  
Molecular Weight ◽  
Partition Coefficient ◽  
Cellulose Nanocrystals ◽  
Partition Coefficients ◽  
Virial Coefficient ◽  
Total Concentration ◽  
Second Virial Coefficient ◽  
Fluorescein Isothiocyanate ◽  
Blue Dextran ◽  
Molecular Weights

The partitioning behaviour of dye-labeled dextrans of high molecular weight in aqueous suspensions of native cellulose nanocrystals was studied. Cellulose concentrations lie in the isotropic–nematic coexistence region. Blue dextrans of various molecular weights and degrees of substitution of dye molecules (anionic Cibacron blue 3G-A) were investigated. Increasing the total concentration of blue dextran and degree of dye substitution led to increasing partition coefficients. Increasing dextran molecular weight resulted in higher partition coefficients, in agreement with theory. Partition coefficients were larger than predicted theoretically using a second virial coefficient approximation. Electrostatic and entropic contributions to the partition coefficient of blue dextran are discussed. Dextrans labeled with neutral fluorescein isothiocyanate did not partition preferentially in this system.Key words: partition coefficient, cellulose nanocrystals, dextrans, degree of substitution, polyelectrolyte.

scholarly journals Molecular Weight, Osmotic Second Virial Coefficient, and Extinction Coefficient of Colloidal CdSe Nanocrystals

2002 ◽  
Vol 106 (21) ◽  
pp. 5500-5505 ◽  
Author(s):  
A. Striolo ◽  
J. Ward ◽  
J. M. Prausnitz ◽  
W. J. Parak ◽  
D. Zanchet ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Extinction Coefficient ◽  
Virial Coefficient ◽  
Second Virial Coefficient ◽  
Cdse Nanocrystals

Solution Properties of Polybutadiene and trans-Polyisoprene Fractions

1963 ◽  
Vol 36 (2) ◽  
pp. 488-501
Author(s):  
W. Cooper ◽  
D. E. Eaves ◽  
G. Vaughan
Keyword(s):  
Molecular Weight ◽  
Light Scattering ◽  
Benzene Solution ◽  
Second Virial Coefficient ◽  
Virial Coefficients ◽  
Γ Radiation ◽  
Branched Polymer ◽  
Butyl Lithium ◽  
Second Virial Coefficients ◽  
Molecular Weights

Abstract Linear polybutadienes, prepared with butyl lithium as catalyst, and polybutadienes branched by exposure to γ-radiation have been fractionated and the fractions examined by osmometry and light scattering. Turbidimetric second virial coefficients (A2τ) of mixed polymer fractions are virtually the same as those of the higher molecular weight components of the mixtures for most compositions. This is true both for mixtures of linear with linear and linear with branched polymer. The higher the molecular weight of the fraction, the greater the effect; the addition of 1 per cent microgel to a linear polymer reduced A2τ by a factor of three. The presence of microgel or high molecular weight branched polymer has been shown to be responsible for the very high molecular weights previously reported for polybutadienes from light scattering measurements. It is conveniently removed by shaking the solutions with calcium sulfate. Second virial coefficients obtained either by light scattering or osmometry are, within the limits of experimental error, uninfluenced by branching in the polymer. In general those factors which lead to increased branching also result in increased polydispersity, and it is the latter which results in the decrease in A2τ. The fall of the osmotic second virial coefficient (A2τ) with molecular weight is much smaller than would be calculated theoretically, and the fall in A2τ is greater than would be expected, notwithstanding the fact that for some of the fractions Mw/Mn<1.1. This indicates that A2τ is sensitive to the low molecular weight species present in the fractions, whereas the reverse must apply to A2τ. Natural or synthetic trans-polyisoprene showed analogous behavior to polybutadiene, although, owing to experimental difficulties, sharp branched fractions could not be obtained. The following viscosity-molecular weight relationships were obtained in benzene solution: [η]=1.45×10−4M0.76 for butyl lithium-catalyzed polybutadienes, and [η]=4.37×10−4M0.65 for natural and synthetic trans-polyisoprenes.

Size, Form and Flexibility of the Rubber Molecule

1962 ◽  
Vol 35 (4) ◽  
pp. 908-917 ◽  
Author(s):  
G. V. Schulz ◽  
A. Mula
Keyword(s):  
Molecular Weight ◽  
Electron Microscope ◽  
Light Scattering ◽  
Virial Coefficient ◽  
Second Virial Coefficient ◽  
Quantitative Measure ◽  
Degree Of Polymerization ◽  
Bromine Content ◽  
Angle Scattering ◽  
Gaussian Density

Abstract Natural rubber can be brominated in dilute cyclohexane solution, whereby the molecular weight, corresponding to the bromine content, increases. For brominated rubber, increasing bromine content makes cyclohexane an increasingly poorer solvent, which is shown by a contraction of the molecule coils and a decrease in the second virial coefficient. Quantitative results were obtained through viscosity and light scattering measurements. Cyclohexane solutions of brominated rubber containing about 43% bromine have a θ point at room temperature. Here the second virial coefficient is zero and the coil has an ideal Gaussian density distribution. In this state the coil diameter is about 1.6 times bigger than for completely free rotation. A comparison of these data with X-ray low angle scattering could yield a quantitative measure of possible molecular branching. Brominated rubber with about one bromine per isoprene residue is a good starting material for the preparation of electron-microscope samples which can be used for the determination of the molecular weight distribution in rubber. The value of the weight average degree of polymerization determined by an electron microscope is in agreement with that determined through (1) light scattering and (2) ultracentrifuge and diffusion measurements. The molecular inhomogeneity of our sample is of the order of 0.5.

Dependence of the Second Virial Coefficient of Aqueous Solutions of Small Non-Electrolytes on Partial Molar Volume and Molecular Weight of the Solutes

1993 ◽  
Vol 46 (6) ◽  
pp. 929 ◽  
Author(s):  
K Kiyosawa
Keyword(s):  
Aqueous Solution ◽  
Molecular Weight ◽  
Aqueous Solutions ◽  
Molar Volume ◽  
Partial Molar Volume ◽  
Virial Coefficient ◽  
Van Der Waals ◽  
Second Virial Coefficient ◽  
Aqueous Systems ◽  
Quadratic Equations

The osmotic pressures of aqueous solutions of small non-electrolytes, namely ethane-1,2-diol, propane-1,2,3-triol, sucrose and raffinose , were found to be expressible by quadratic equations of the molar concentration, which indicate that these aqueous systems involve no term higher than the second virial coefficient A2. Analysis has shown that A2 mainly does not arise from non-ideality of the aqueous solutions, but its magnitude depends on the partial molar volume of the solute, more precisely on the molecular weight or van der Waals radius or volume of the solute in the aqueous solution.

Sign in / Sign up

Export Citation Format

Share Document